1) From what I understand, both systems use ISO connectors instead of the quadlock present on the 9N3. However, I know that the MCD was offered as an option on the 9N3 from the factory. Is this a different unit with a quadlock connector, or is the wiring loom modified to have ISO connectors in 9N3's with this option fitted?

2) From photos of the MCD wiring diagram (above) it appears that blocks A and B are ISO terminals, and that C is for a CD changer etc. I'm having trouble finding the purpose of block D. Is it necessary for operation of the unit or is it to allow the unit to communicate with the digital screen present in the dash cluster of some cars (like Golfs)?
3) Is there any improvement in sound quality with the MCD over the standard RCD200? I'm tempted to just fit it as a radio upgrade lol.
Thanks in advance

